yeewong_su said:
Maybe you mean that you need a power on reset circuit. it can give you a info whether the power is ok
Hi, do you mean a circuit like voltage detector (like LMS33460)? what if the supply voltage drops to a level (less than 2V in my case) that both bandgap and comparator are not able to work, at this moment, the output signal is uncertain, it will be 0.5v or something like that, so how to make sure when VDD drops, the circuit can give a reliable 0V output? Thanks.